Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L3/00—Compositions of starch, amylose or amylopectin or of their derivatives or degradation products
  • C08L3/02—Starch; Degradation products thereof, e.g. dextrin
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/08—Cellulose derivatives
  • C08L1/10—Esters of organic acids, i.e. acylates
  • C08L1/12—Cellulose acetate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/24—Acids; Salts thereof
  • C08K3/26—Carbonates; Bicarbonates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/08—Cellulose derivatives
  • C08L1/10—Esters of organic acids, i.e. acylates
  • C08L1/14—Mixed esters, e.g. cellulose acetate-butyrate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2201/00—Properties
  • C08L2201/06—Biodegradable
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials

Definitions

• Biodegradable compositions comprising starch and polysaccharide esters
• the present invention relates to biodegradable compositions comprising starch and polysaccharide esters, suitable for producing moulded articles which can decompose rapidly during composting.
• compositions containing starch and cellulose esters consists of the provision of compositions having good biodegradability which are suitable for the production of shaped articles having an adequate capacity to decompose during composting .
• compositions comprising starch and cellulose esters which have improved compatibility between the polymeric components but which do not have adequate biodegradability are described in the patent literature.
• EP-A-0 722 980 describes compositions in which the starch and the cellulose ester are rendered more compatible with one another with the use of specific phase compatibilizing agents which are selected from various classes of polymeric substances, and which - in addition to improving compatibility - also have the effect of improving biodegradability by virtue of the high level of dispersion conferred on the starch in the cellulose-ester matrix.
• articles produced from the compositions still have too low a decomposition rate during composting. It has now surprisingly been found that it is possible considerably to increase the biodegradability of articles produced from compositions comprising partially or completely destructurized and/or complexed starch and polysaccharide esters, preferably cellulose esters, and consequently their ability to decompose during composting.
• the decomposition times for the articles produced can be reduced to less than two months in standard composting conditions .
• compositions of the present invention comprising starch and a polysaccharide ester and preferably a cellulose ester or a starch ester are characterized by a microstructure in which the ester constitutes the matrix and the fraction of destructurized and/or dispersed starch constitutes the dispersed phase, with a numeric mean dimension of the domains or dispersed particles of less than 1 ⁇ m, preferably less than 0.5 ⁇ m, and in that they contain an additive which can increase and maintain at values of 4 or more the pH of a solution obtained by immersing granules of the composition in water at ambient temperature for 1 hour with the use of a water: granules ratio of 10:1 by weight.
• the additive which has the above-mentioned capability to control the pH, has the effect of considerably increasing the biodegradability of the compositions by neutralizing the acid resulting from hydrolysis of the cellulose ester in composting conditions .
• Any substance insoluble in water and having the above-mentioned capability may be a suitable additive .
• Examples of additives are carbonates and hydroxides of alkaline-earth metals such as CaCC>3 , MgCC>3 , Mg(OH)2- CaC0 3 is the preferred additive.
• compositions comprise starch and the polysaccharide ester plasticized with a plasticizer in a quantity of from 10 to 40% by weight, in a ratio by weight of from 1:0.6 to 1:18, preferably from 1:2 to 1:3.
• the additive is present in a quantity of from 0.5 to 30%, preferably from 5 to 20%, by weight relative to the weight of the starch and of the plasticized polysaccharide ester.
• Quantities greater than 30% by weight may be used without any significant further improvement .
• Too large a quantity of additive may have an adverse effect on the mechanical properties of the compositions.
• compositions may also comprise a plasticizer for the starch phase, used in a quantity of from 0.5 to 50% by weight, relative to the weight of the starch.
• additives belonging to the following classes are used:
• e) polymers capable of complexing starch such as ethylene/vinyl alcohol or ethylene/acrylic acid copolymers, aliphatic polyesters and polyamides .
• the additives of type a) are preferably obtained by grafting aliphatic chains derived from vegetable or animal fats such as oleic, lauric, myristic, palmitic, stearic, linoleic and ricinoleic acids having terminal groups such as carboxyl groups, esters or salts to facilitate the grafting of the chains .
• polymers compatible with the cellulose esters are :
• DS starch esters with various DS values, such as acetates, starch esters with various DS values, such as products of the reaction of starch with ethylene or propylene glycol , partially hydrolyzed polyvinyl acetate, aliphatic polyesters and aliphatic/aromatic copolyesters .
• the number of grafted chains is between 0.1 and 100, preferably from 0.2 to 50, more preferably from 0.3 to 20 grafted chains per 100 monomeric units in the polymeric chain.
• additives of type b) and type c) are the copolymers which can be produced from aliphatic polyesters such as polycaprolactones and polyethylene succinates .
• a caprolactone-urethane copolymer marketed by Goodrich with the trade mark Estane, grade 54351 is representative of the copolymers of class b) .
• the additives are present in quantities of from 0.1 to 20% by weight, preferably from 0.5 to 10%, relative to the sum of the weight of the starch and of the plasticized polysaccharide ester.
• compositions of the invention may contain synthetic polymers in a quantity up to 30% by weight, preferably less than 10%, of polyvinyl alcohol, polyvinyl acetate, thermoplastic polyesters such as polycaprolactone, copolymers of caprolactone with isocyanates, polymers of lactic acid, polyethylene or polybutylene and, in general, polyalchylen adipate, sebacate, and azelate .
• synthetic polymers in a quantity up to 30% by weight, preferably less than 10%, of polyvinyl alcohol, polyvinyl acetate, thermoplastic polyesters such as polycaprolactone, copolymers of caprolactone with isocyanates, polymers of lactic acid, polyethylene or polybutylene and, in general, polyalchylen adipate, sebacate, and azelate .
• the starch which is used to prepare the composition is a natural starch extracted from various plants such as maize, wheat, potato, tapioca and cereal starch.
• the term starch also includes starches with a high amylopectin content ("waxy" starches), starches with a high amylose content, chemically and physically modified starches, starches in which the type and concentration of the cations associated with phosphate groups are modified, starch ethoxylate, starch acetates, cationic starches, hydrolyzed starches, oxidized and cross-linked starches.
• the final composition contains starch which is partially or completely destructurized and/or complexed.
• destructurized starch is intended starch which has lost its granular structure (that means absence of Maltese crosses which is visible by optical microscopy in polarized light with magnification in the range of 250 — 700 x) .
• starch As complexed starch is intended starch showing a band in second derivative FTIR around at 946 — 947 cm -1 after removal of the cellulose or starch ester in chloroform (with high starch concentrations without extraction of the cellulose or starch ester) or showing also peaks around 12- 13 and 20 of 2 ⁇ (2 theta) in X-ray diffraction experiments.
• Representative cellulose and starch esters comprise cellulose acetates, propionates and/or butyrates with various degrees of substitution.
• Cellulose acetate with a DS of from 1.5 to 2.5 is preferred.
• the plasticizer usable for the cellulose ester is preferably selected from the following compounds :
• glycerol esters with aliphatic acids containing up to 6 carbon atoms particularly diacetin and triacetin, esters of citric acid, particularly trimethyl or triethyl citrate, as well as acetyl-triethyl citrate, dialkyl esters of tartaric acid, aliphatic-acid esters, lactones and lactides, dialkyl esters of aliphatic acids such as those obtained from oxalic, glutaric, adipic, sebacic, suberic, azelaic acids, preferably dibutyl adipate and dibutyl sebacate , dialkyl esters of aromatic acids in which the alkyl group contains from 1 to 10 carbon atoms, particularly dimethyl phthalate, diethyl phthalate, methoxyethyl phthalate and ethoxyethyl phthalate, polyethylene glycol adipate, glutarate or sebacate, alkyl and aryl phosphate
• the preferred plasticizers are those which act as plasticizers both for the starch phase and for the cellulose ester phase. Acetins belong to this preferred class.
• the plasticizers for the starch comprise water, glycerol, glycerol ethoxylate, ethylene glycol or propylene glycol , polyethylene glycol, polypropylene glycol, 1, 2-propandiol, 1 , 3 -propandiol , 1,2-, 1,3-, 1, 4-butandiol , 1,6-, 1,5- hexandiol, sorbitol diethoxylate, and trimethylolpropane monoethoxylate .
• the starch is normally plasticized directly during the mixing stage in a mixture with all of the other components .
• the preparation of the composition of the invention comprises the mixing of the components in a heated extruder or in any closed container which can ensure conditions of temperature and of shear stress adequate to render the starch and cellulose ester components compatible with one another from a rheological point of view, operating at a temperature of between 80 and 210°C in the presence of water and plasticizers .
• the preferred method of preparing the compositions comprises : a first step consisting in passing the components through an extruder with times spent in the extruder of the order of from 2 to 50 seconds, during which the starch and the cellulose ester are subjected to bulking under the effect of the plasticizer and possibly of added water, operating at a temperature of between 80 and 180°C, a mixing step, during which the mixture of the previous step is subjected to shear stress conditions suitable in particular for rendering the viscosities of the molten cellulose ester and starch similar, if the starting viscosities are different, an optional degassing step to produce a molten mass with a water content of less than 6% by weight which ensures, amongst other things, that bubbles do not form in the extruded product. If expanded materials are to be produced, the water content may be higher than 6% and may reach 18-20% by weight.
• the resulting molten material is extruded to form pellets from which articles are produced by means of any conventional technique, or the composition may be extruded directly to produce moulded or injection-moulded articles.
• compositions of the present invention are suitable for the production of foams, foamed extruded containers, foamed extruded sheets, moulded foams, injection-moulded articles such as toys and disposable cutlery and, in general, articles for any use which requires decomposition times no longer than two months during composting.
• foams foamed extruded containers, foamed extruded sheets, moulded foams, injection-moulded articles such as toys and disposable cutlery and, in general, articles for any use which requires decomposition times no longer than two months during composting.
• Examples 1-4 are comparative examples; Examples 5-7 are in accordance with the invention.
• the temperature profile of the sixteen controlled-temperature zones was as follows:
• the rate of rotation of the screw was 120 rpm.
• the pellets produced by the extruder were supplied to a Sandretto Series 60 injection press to produce shaped test samples.
• the samples were examined with regard to their surface quality by optical microscopy or by SEM electron microscopy.
• the samples were also tested to determine the biodegradation rate.
• Aceplast LS is a cellulose acetate with a degree of substitution of 2.5, marketed by Societa Acetati S.p.A., of Verbania, Italy.
• CAB is a cellulose butyrate/acetate marketed by Eastman Chemicals under the mark CAB 831-20.
• the additives indicated in the table were produced from starch acetate (SAC) with DS 1.3 and 2.1, by grafting lauryl radicals in quantities of 4.2 and 3.2 radicals per 100 monomeric units of SAC.
• the grafting was carried out with the use of lauric acid chloride in dimethyl acetamide .
• the compatibilizing agent was precipitated with ethyl ether.
• the biodegradability was tested by recording the loss of weight of the samples which were enclosed in a polypropylene net (with 1 mm mesh) and were incorporated in a substrate of an aged compost with 55% humidity and heated to 50°C in an incubator. A plurality of samples was loaded, that is, one sample per net so that the course of the degradation over time could be followed. For each sample, 50 g of compost was used. The results are given in Table 2. TABLE 2

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Biological Depolymerization Polymers (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Confectionery (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

Priority Applications (14)

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Citations (3)

• 1998
  • 1998-09-01 IT IT1998TO000735A patent/IT1303553B1/it active IP Right Grant
• 1999
  • 1999-08-31 WO PCT/EP1999/006390 patent/WO2000012616A1/en not_active Application Discontinuation
  • 1999-08-31 AU AU58570/99A patent/AU755074B2/en not_active Ceased
  • 1999-08-31 ES ES99946073T patent/ES2195611T3/es not_active Expired - Lifetime
  • 1999-08-31 CA CA002342174A patent/CA2342174C/en not_active Expired - Fee Related
  • 1999-08-31 BR BR9913491-8A patent/BR9913491A/pt not_active IP Right Cessation
  • 1999-08-31 KR KR1020017002633A patent/KR20010073073A/ko not_active Application Discontinuation
  • 1999-08-31 JP JP2000567622A patent/JP4303890B2/ja not_active Expired - Fee Related
  • 1999-08-31 US US09/786,189 patent/US6730724B1/en not_active Expired - Lifetime
  • 1999-08-31 DK DK99946073T patent/DK1109858T3/da active
  • 1999-08-31 DE DE69907224T patent/DE69907224T2/de not_active Expired - Lifetime
  • 1999-08-31 AT AT99946073T patent/ATE238386T1/de active
  • 1999-08-31 EP EP99946073A patent/EP1109858B1/en not_active Expired - Lifetime
  • 1999-08-31 ZA ZA200102222A patent/ZA200102222B/en unknown
  • 1999-08-31 MX MXPA01002196A patent/MXPA01002196A/es not_active Application Discontinuation
  • 1999-08-31 IL IL14166499A patent/IL141664A0/xx unknown
  • 1999-08-31 CN CNB998129089A patent/CN1225494C/zh not_active Expired - Fee Related
• 2001
  • 2001-02-28 NO NO20011039A patent/NO328637B1/no not_active IP Right Cessation
  • 2001-03-30 HR HR20010241A patent/HRP20010241A2/hr not_active Application Discontinuation

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